[unreadable] [unreadable] Significant advances have been made in developing ontologies for medical knowledge over the last 40 years, resulting in advances in standardization, information sharing and automation not previously possible in medicine. In contrast, the development of ontologies for behavioral medicine is decades behind, even though behavioral factors such as smoking, poor diet and physical inactivity are the primary determinants of half of the Healthy People 2010 Leading Health Indicators. [unreadable] [unreadable] In this exploratory/developmental project, a suite of software tools for developing and deploying automated dialog-based health behavior change interventions based on computational ontologies of concepts from behavioral medicine will be integrated and used to build three demonstration systems in the areas of physical activity and healthy eating promotion. The tools will be used to create an ontology of concepts relevant to health behavior change (specifically, counseling techniques from Motivational Interviewing used within the framework of the Transtheoretical Model), including a task model of process and techniques for health behavior change counseling. The tools will be used to build a system that provides a two-month physical activity promotion intervention designed for daily contact with subjects on their home computers. Following usability evaluations, a second system for promotion of fruit and vegetable consumption, and a third system for promotion of both physical activity and fruit and vegetable consumption, will be developed in order to demonstrate the reusability of the ontological models. The run-time dialog system will be based on a dialog planner informed by theories of human collaborative behavior, and on FitTrack, a client-server architecture for delivering health behavior change interventions over the Internet to subjects' home- computers via an animated counselor. The usability, fidelity to behavior change theory, and efficacy of the resulting intervention systems will be evaluated in a three-arm randomized pilot study. The ontology will be developed in Prot[unreadable]g[unreadable] and, along with all task models and other software developed for this effort, will be made publicly available at the conclusion of the project. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]